Ultrasound images are typically generated and displayed as two-dimensional (2-D) image slices. For example, with reference to FIG. 1A, a conventional ultrasound imaging system 100 comprising a transducer 102 and a control system 104 are configured to obtain two-dimensional imaging information 106 and display two-dimensional imaging slices 108. However, it is often desirable to acquire a whole volume of data in the form of multiple image planes and render it in a three-dimensional (3-D) format, such as for viewing a fetus. Acquiring multiple image slices can be performed by moving the imaging probe in a manner to produce volumetric information. The quality of the computer-rendered 3-D image (the output) is closely related to spatial sampling of the volume-of-interest (the input data). Specifically, for ease and accuracy of the 3-D reconstruction, it would be desirable for the input image planes to be configured a minimum distance apart to avoid spatial aliasing, as well as in a defined attitude and position to avoid gross spatial distortions in rendering based on assumptions about the probe's motion. Unfortunately, prior art methodologies cannot provide such features.
For example, one shortcoming of so-called “free-hand” 3-D scanning is the lack of precision and repeatability in which the 3-D volume is interrogated due to spatially and temporally imprecise angular and linear displacements. As a result a number of pitfalls exist. As a first example, if sensors record the attitude and position of the probe, it is still possible to over- and/or under-sample the volume-of-interest. Second, even if the volume is adequately sampled, the random nature of the input data orientation requires excessive mathematical interpolations to compute a 3-D image in a uniform output grid. Third, if no sensors are used image frame correlation methods cannot accurately ascertain the relative orientation of image planes. Finally, even if six-degree-of-freedom sensors are utilized, such sensors are expensive and have limited range. In fact, what is desirable is motion having a single degree-of-freedom.
Some methodologies have used mechanical fixtures with water baths (for acoustic coupling) as well as motorized assemblies to move an imaging probe in one dimension. However, such mechanisms can be extremely cumbersome and unwieldy for human scanning and may pose safety hazards if designed improperly.